As I understand it the idea is not necessarily to stop all dissent / awareness, but that it's useful to be able to slow the spread of "rumours" / incendiary information when it is spreading virally. This gives authorities time to come up with a response if required.

While I personally wouldn't want to live in a country which does this, the flip side of unrestricted virality in countries that culturally might not be prepared for it are events like https://en.wikipedia.org/wiki/Indian_WhatsApp_lynchings

Given that the US controls much of what happens on the Internet, another issue for many countries (not China so much) is that without controls they become extremely vulnerable to US influence campaigns and "colour revolutions".

I predict that all countries will end up with something like the GFW eventually because there's basically no other way for governments to achieve "Internet sovereignty" (enforce laws regarding users and publishers on the web). The US might be last to do this because it is in the doubly privileged position of a) being able to exert significant pressure on other countries and b) being able to apply regulation to major US-based Internet companies using their own legal system.